The invention relates to the plating of metal, specifically strips of metal and is particularly useful in the spot plating of selected small areas on the kind of strips that are called lead frames. Lead frames are used to mount semiconductor chips and the like.
In the prior art, lead frames are formed from a continuous web of metal which is spot plated at the desired locations before it is cut up and shaped for use. Such a reel-to-reel operation is disclosed in U.S. Pat. No. 3,723,283. This process can be wasteful since the cutting and stamping processes may damage the product after it has been plated with precious metals. Another prior art approach is to first cut and shape or chemically etch the lead frames into discrete, nearly finished, short strips and then plate the precious metals only on inspected and acceptable strips. However, this is cumbersome and slow since the individual strips must be loaded onto racks and the racks immersed in plating tanks to deposit the precious metals. The present invention contemplates an entirely new approach to the plating of lead frames that avoids the above difficulties.